OVERVIEW OF B1 DEFICIENCY
- Vitamin B1 (thiamine) is water-soluble, comprised of a pyrimidine and a thiazole ring.
- Dietary sources: Whole-grain cereals, whole-wheat bread, brown rice, legumes, yeast, fresh meats (especially pork).
- Stability: Destroyed by high temperature and alkaline pH (cooking/baking/pasteurization can reduce bioactivity).
- Absorption: Occurs in the jejunum and ileum; once in blood, thiamine binds albumin and enters cells by passive diffusion + active transport.
- Tissue distribution: Heart, skeletal muscle, brain, liver, kidney.
- Half-life & storage: Biologic half-life 10–20 days; no large tissue depot → continuous dietary intake required.
BIOCHEMICAL ROLE
- Cofactor for enzymes in carbohydrate and amino acid metabolism:
- Converts pyruvate to acetyl coenzyme A.
- Functions in the pentose phosphate pathway.
- Essential for normal nerve conduction.
BERIBERI
- Cause: Nutritional deficiency in thiamine.
- Populations:
- Breastfed infants of thiamine-deficient mothers.
- Children/adults consuming polished rice or high alcohol → poor thiamine intake.
- Clinical features:
- Infantile beriberi (by ~2 months):
- CNS issues: vomiting, nystagmus, purposeless movements, seizures.
- Cardiac disease: cardiomegaly, tachycardia, cyanosis.
- Sudden death if untreated.
- Adult beriberi:
- Dry beriberi:
- Predominantly neurologic.
- Symmetric peripheral neuropathy (distal paresthesias), muscle weakness (foot/wrist drop), muscle wasting, possible aphonia, emaciation.
- Wet beriberi:
- Predominantly cardiac.
- Cardiomegaly, congestive heart failure signs (dyspnea, orthopnea, edema, tachycardia).
- Dry beriberi:
- Infantile beriberi (by ~2 months):
- Treatment:
- Supportive care + thiamine supplementation:
- IV or IM: 50–100 mg daily for ~2 weeks.
- Then oral dose: ~10 mg/day until full recovery.
- Evaluate for coexisting vitamin deficiencies.
- Supportive care + thiamine supplementation:
WERNICKE-KORSAKOFF SYNDROME
- Most severe thiamine deficiency in adults.
- Wernicke encephalopathy:
- Ophthalmoplegia (6th cranial nerve palsy), nystagmus, ataxia, confusion → may progress to coma.
- Commonly in alcoholics (poor thiamine intake + depletion).
- Requires urgent treatment: 50 mg IV thiamine daily, then oral.
- Korsakoff syndrome:
- Chronic phase after Wernicke encephalopathy.
- Marked by impaired short-term memory, confabulation.
DIAGNOSIS
- Blood thiamine measurement:
- Reference range: 80–150 nmol/L.
- Levels <80 nmol/L suggest deficiency.
PREVENTION
- Recommended dietary allowance (RDA) for thiamine:
- Men: 1.2 mg/day
- Women: 1.0 mg/day (1.4 mg in pregnancy/lactation)
- Easy to obtain from a nutritionally balanced diet rich in:
- Whole grains
- Legumes
- Yeast
- Fresh meats